Using multiple signals to detect touch input

ABSTRACT

Detecting a location of a touch input is disclosed. Each of a plurality of transmitters coupled to a propagating medium emits a signal that is distinguishable from other signals emitted from other transmitters. The signals from the transmitters are received from at least one receiver coupled to the propagating medium to detect the location of the touch input on a surface of the propagating medium as indicated by an effect of the touch input on each of the distinguishable signals.

CROSS REFERENCE TO OTHER APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/462,581 entitled USING MULTIPLE SIGNALS TO DETECT TOUCHINPUT filed Mar. 17, 2017, which is incorporated herein by reference forall purposes, which is a continuation of U.S. patent application Ser.No. 14/033,316 entitled USING MULTIPLE SIGNALS TO DETECT TOUCH INPUTfiled Sep. 20, 2013, now U.S. Pat. No. 9,639,213, which is incorporatedherein by reference for all purposes, which is a continuation in part ofU.S. patent application Ser. No. 13/451,288 entitled METHOD ANDAPPARATUS FOR ACTIVE ULTRASONIC TOUCH DEVICES filed Apr. 19, 2012, nowU.S. Pat. No. 9,477,350, which is incorporated herein by reference forall purposes, which claims priority to U.S. Provisional PatentApplication No. 61/479,331, entitled METHOD AND APPARATUS FOR ACTIVEULTRASONIC TOUCH DEVICES filed Apr. 26, 2011 and claims priority to U.S.Provisional Patent Application No. 61/594,255 entitled TOUCH SCREENDEVICE SIGNAL DESIGNS AND METHODS filed Feb. 2, 2012, all of which areincorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

Various technologies have been used to detect a touch input on a displayarea. The most popular technologies today include capacitive andresistive touch detection technology. Using resistive touch technology,often a glass panel is coated with multiple conductive layers thatregister touches when physical pressure is applied to the layers toforce the layers to make physical contact. Using capacitive touchtechnology, often a glass panel is coated with material that can hold anelectrical charge sensitive to a human finger. By detecting the changein the electrical charge due to a touch, a touch location can bedetected. However, with resistive and capacitive touch detectiontechnologies, the glass screen is required to be coated with a materialthat reduces the clarity of the glass screen. Additionally, because theentire glass screen is required to be coated with a material,manufacturing and component costs can become prohibitively expensive aslarger screens are desired.

Another type of touch detection technology includes bending wavetechnology. One example includes the Elo Touch Systems Acoustic PulseRecognition, commonly called APR, manufactured by Elo Touch Systems of301 Constitution Drive, Menlo Park, Calif. 94025. The APR systemincludes transducers attached to the edges of a touchscreen glass thatpick up the sound emitted on the glass due to a touch. However, thesurface glass may pick up other external sounds and vibrations thatreduce the accuracy and effectiveness of the APR system to efficientlydetect a touch input. Another example includes the Surface AcousticWave-based technology, commonly called SAW, such as the Elo IntelliTouchPlus™ of Elo Touch Systems. The SAW technology sends ultrasonic waves ina guided pattern using reflectors on the touch screen to detect a touch.However, sending the ultrasonic waves in the guided pattern increasescosts and may be difficult to achieve. Detecting additional types ofinputs, such as multi-touch inputs, may not be possible or may bedifficult using SAW or APR technology. Therefore there exists a need fora better way to detect an input on a surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a block diagram illustrating an embodiment of a system fordetecting a surface disturbance.

FIG. 2 is a block diagram illustrating an embodiment of a system fordetecting a touch input.

FIG. 3 is a flow chart illustrating an embodiment of a process forcalibrating and validating touch detection.

FIG. 4 is a flow chart illustrating an embodiment of a process fordetecting a user touch input.

FIG. 5 is a flow chart illustrating an embodiment of a process fordetermining a location associated with a disturbance on a surface.

FIG. 6 is a flow chart illustrating an embodiment of a process fordetermining a location associated with a disturbance.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Detecting a location of a touch input is disclosed. For example, a usertouch input on a glass surface of a display screen is detected. In someembodiments, a plurality of transmitters coupled to a propagating medium(e.g., glass) emits signals that are distinguishable from other signalsemitted from other transmitters. For example, a signal such as anacoustic or ultrasonic signal is propagated freely through a propagatingmedium with a touch input surface from each transmitter coupled to thepropagating medium. In some embodiments, the signals emitted by thetransmitters are distinguishable from each other by varying a phase ofthe signals (e.g., code division multiplexing, code division multipleaccess (CDMA), spread spectrum multiple access (SSMA)), a frequencyrange of the signals (e.g., frequency division multiplexing, frequencydivision multiple access (FDMA)) or a timing of the signals (e.g., timedivision multiplexing, time division multiple access (TDMA)).

At least one receiver is coupled to the propagating medium, and thereceiver is configured to receive the signals from the transmitters todetect the location of the touch input on a surface of the propagatingmedium as indicated by the effect of the touch input on each of thedistinguishable signals. For example, when the surface of thepropagating medium is touched, the emitted signals propagating throughthe propagating medium are disturbed (e.g., the touch causes aninterference with the propagated signals). In some embodiments, byprocessing the received signals and comparing it against correspondingexpected signals without the disturbance, a location on the surfaceassociated with the touch input is at least in part determined. Forexample, a relative time difference between when the disturbance wasdetected in the received signals is used to determine the touch inputlocation on the surface. In various embodiments, the touch inputincludes a physical contact to a surface using a human finger, pen,pointer, stylus, and/or any other body parts or objects that can be usedto contact or disturb the surface. In some embodiments, the touch inputincludes an input gesture and/or a multi-touch input.

In some embodiments, the received signal is used to determine one ormore of the following associated with a touch input: a gesture, acoordinate position, a time, a time frame, a direction, a velocity, aforce magnitude, a proximity magnitude, a pressure, a size, and othermeasurable or derived parameters. In some embodiments, by detectingdisturbances of a freely propagated signal, touch input detectiontechnology can be applied to larger surface regions with less or noadditional cost due to a larger surface region as compared to certainprevious touch detection technologies. Additionally, the opticaltransparency of a touch screen may not have to be affected as comparedto resistive and capacitive touch technologies. Merely by way ofexample, the touch detection described herein can be applied to avariety of objects such as a kiosk, an ATM, a computing device, anentertainment device, a digital signage apparatus, a cell phone, atablet computer, a point of sale terminal, a food and restaurantapparatus, a gaming device, a casino game and application, a piece offurniture, a vehicle, an industrial application, a financialapplication, a medical device, an appliance, and any other objects ordevices having surfaces.

FIG. 1 is a block diagram illustrating an embodiment of a system fordetecting a touch input surface disturbance. In some embodiments, thesystem shown in FIG. 1 is included in a kiosk, an ATM, a computingdevice, an entertainment device, a digital signage apparatus, a cellphone, a tablet computer, a point of sale terminal, a food andrestaurant apparatus, a gaming device, a casino game and application, apiece of furniture, a vehicle, an industrial application, a financialapplication, a medical device, an appliance, and any other objects ordevices having surfaces. Propagating signal medium 102 is coupled totransmitters 104, 106, 108, and 110 and receivers/sensors 112, 114, 116,and 118. The locations where transmitters 104, 106, 108, and 110 andsensors 112, 114, 116, and 118 have been coupled to propagating signalmedium 102, as shown in FIG. 1, are merely an example. Otherconfigurations of transmitter and sensor locations may exist in variousembodiments. Although FIG. 1 shows sensors located adjacent totransmitters, sensors may be located apart from transmitters in otherembodiments. In some embodiments, a single transducer is used as both atransmitter and a sensor. In various embodiments, the propagating mediumincludes one or more of the following: panel, table, glass, screen,door, floor, whiteboard, plastic, wood, steel, metal, semiconductor,insulator, conductor, and any medium that is able to propagate anacoustic or ultrasonic signal. For example, medium 102 is glass of adisplay screen. A first surface of medium 102 includes a surface areawhere a user may touch to provide a selection input and a substantiallyopposite surface of medium 102 is coupled to the transmitters andsensors shown in FIG. 1. In various embodiments, a surface of medium 102is substantially flat, curved, or combinations thereof and may beconfigured in a variety of shapes such as rectangular, square, oval,circular, trapezoidal, annular, or any combination of these, and thelike.

Examples of transmitters 104, 106, 108, and 110 include piezoelectrictransducers, electromagnetic transducers, transmitters, sensors, and/orany other transmitters and transducers capable of propagating a signalthrough medium 102. Examples of sensors 112, 114, 116, and 118 includepiezoelectric transducers, electromagnetic transducers, laser vibrometertransmitters, and/or any other sensors and transducers capable ofdetecting a signal on medium 102. In some embodiments, the transmittersand sensors shown in FIG. 1 are coupled to medium 102 in a manner thatallows a user's input to be detected in a predetermined region of medium102. Although four transmitters and four sensors are shown, any numberof transmitters and any number of sensors may be used in otherembodiments. For example, two transmitters and three sensors may beused. In some embodiments, a single transducer acts as both atransmitter and a sensor. For example, transmitter 104 and sensor 112represent a single piezoelectric transducer. In the example shown,transmitters 104, 106, 108, and 110 each may propagate a signal throughmedium 102. A signal emitted by a transmitter is distinguishable fromanother signal emitted by another transmitter. In order to distinguishthe signals, a phase of the signals (e.g., code division multiplexing),a frequency range of the signals (e.g., frequency divisionmultiplexing), or a timing of the signals (e.g., time divisionmultiplexing) may be varied. One or more of sensors 112, 114, 116, and118 receive the propagated signals. In another embodiment, thetransmitters/sensors in FIG. 1 are attached to a flexible cable coupledto medium 102 via an encapsulant and/or glue material and/or fasteners.

Touch detector 120 is connected to the transmitters and sensors shown inFIG. 1. In some embodiments, detector 120 includes one or more of thefollowing: an integrated circuit chip, a printed circuit board, aprocessor, and other electrical components and connectors. Detector 120determines and sends signals to be propagated by transmitters 104, 106,108, and 110. Detector 120 also receives the signals detected by sensors112, 114, 116, and 118. The received signals are processed by detector120 to determine whether a disturbance associated with a user input hasbeen detected at a location on a surface of medium 102 associated withthe disturbance. Detector 120 is in communication with applicationsystem 122. Application system 122 uses information provided by detector120. For example, application system 122 receives from detector 120 acoordinate associated with a user touch input that is used byapplication system 122 to control a software application of applicationsystem 122. In some embodiments, application system 122 includes aprocessor and/or memory/storage. In other embodiments, detector 120 andapplication system 122 are at least in part included/processed in asingle processor. An example of data provided by detector 120 toapplication system 122 includes one or more of the following associatedwith a user indication: a location coordinate of a surface of medium102, a gesture, simultaneous user indications (e.g., multi-touch input),a time, a status, a direction, a velocity, a force magnitude, aproximity magnitude, a pressure, a size, and other measurable or derivedinformation.

FIG. 2 is a block diagram illustrating an embodiment of a system fordetecting a touch input. In some embodiments, touch detector 202 isincluded in touch detector 120 of FIG. 1. In some embodiments, thesystem of FIG. 2 is integrated in an integrated circuit chip. Touchdetector 202 includes system clock 204 that provides a synchronoussystem time source to one or more other components of detector 202.Controller 210 controls data flow and/or commands between microprocessor206, interface 208, DSP engine 220, and signal generator 212. In someembodiments, microprocessor 206 processes instructions and/orcalculations that can be used to program software/firmware and/orprocess data of detector 202. In some embodiments, a memory is coupledto microprocessor 206 and is configured to provide microprocessor 206with instructions. Signal generator 212 generates signals to be used topropagate signals such as signals propagated by transmitters 104, 106,108, and 110 of FIG. 1. For example, signal generator 212 generatespseudorandom binary sequence signals that are converted from digital toanalog signals. Different signals (e.g., a different signal for eachtransmitter) may be generated by signal generator 212 by varying a phaseof the signals (e.g., code division multiplexing), a frequency range ofthe signals (e.g., frequency division multiplexing), or a timing of thesignals (e.g., time division multiplexing). Driver 214 receives thesignal from generator 212 and drives one or more transmitters, such astransmitters 104, 106, 108, and 110 of FIG. 1, to propagate signalsthrough a medium.

A signal detected from a sensor such as sensor 112 of FIG. 1 is receivedby detector 202 and signal conditioner 216 conditions (e.g., filters)the received analog signal for further processing. For example, signalconditioner 216 receives the signal outputted by driver 214 and performsecho cancellation of the signal received by signal conditioner 216. Theconditioned signal is converted to a digital signal by analog-to-digitalconverter 218. The converted signal is processed by digital signalprocessor engine 220. For example, DSP engine 220 separates componentscorresponding to different signals propagated by different transmittersfrom the received signal and each component is correlated against areference signal. The result of the correlation may be used bymicroprocessor 206 to determine a location associated with a user touchinput. For example, microprocessor 206 compares relative differences ofdisturbances detected in signals originating from different transmittersand/or received at different receivers/sensors to determine thelocation. Interface 208 provides an interface for microprocessor 206 andcontroller 210 that allows an external component to access and/orcontrol detector 202. For example, interface 208 allows detector 202 tocommunicate with application system 122 of FIG. 1 and provides theapplication system with location information associated with a usertouch input.

FIG. 3 is a flow chart illustrating an embodiment of a process forcalibrating and validating touch detection. In some embodiments, theprocess of FIG. 3 is used at least in part to calibrate and validate thesystem of FIG. 1 and/or the system of FIG. 2. At 302, locations ofsignal transmitters and sensors with respect to a surface aredetermined. For example, locations of transmitters and sensors shown inFIG. 1 are determined with respect to their location on a surface ofmedium 102. In some embodiments, determining the locations includesreceiving location information. In various embodiments, one or more ofthe locations may be fixed and/or variable.

At 304, signal transmitters and sensors are calibrated. In someembodiments, calibrating the transmitter includes calibrating acharacteristic of a signal driver and/or transmitter (e.g., strength).In some embodiments, calibrating the sensor includes calibrating acharacteristic of a sensor (e.g., sensitivity). In some embodiments, thecalibration of 304 is performed to optimize the coverage and improvesignal-to-noise transmission/detection of a signal (e.g., acoustic orultrasonic) to be propagated through a medium and/or a disturbance to bedetected. For example, one or more components of the system of FIG. 1and/or the system of FIG. 2 are tuned to meet a signal-to-noiserequirement. In some embodiments, the calibration of 304 depends on thesize and type of a transmission/propagation medium and geometricconfiguration of the transmitters/sensors. In some embodiments, thecalibration of step 304 includes detecting a failure or aging of atransmitter or sensor. In some embodiments, the calibration of step 304includes cycling the transmitter and/or receiver. For example, toincrease the stability and reliability of a piezoelectric transmitterand/or receiver, a burn-in cycle is performed using a burn-in signal. Insome embodiments, the step of 304 includes configuring at least onesensing device within a vicinity of a predetermined spatial region tocapture an indication associated with a disturbance using the sensingdevice. The disturbance is caused in a selected portion of the inputsignal corresponding to a selection portion of the predetermined spatialregion.

At 306, surface disturbance detection is calibrated. In someembodiments, a test signal is propagated through a medium such as medium102 of FIG. 1 to determine an expected sensed signal when no disturbancehas been applied. In some embodiments, a test signal is propagatedthrough a medium to determine a sensed signal when one or morepredetermined disturbances (e.g., predetermined touch) are applied at apredetermined location. Using the sensed signal, one or more componentsmay be adjusted to calibrate the disturbance detection.

At 308, a validation of a touch detection system is performed. Forexample, the system of FIG. 1 and/or FIG. 2 is tested usingpredetermined disturbance patterns to determine detection accuracy,detection resolution, multi-touch detection, and/or response time. Ifthe validation fails, the process of FIG. 3 may be at least in partrepeated and/or one or more components may be adjusted before performinganother validation.

FIG. 4 is a flow chart illustrating an embodiment of a process fordetecting a user touch input. In some embodiments, the process of FIG. 4is at least in part implemented on touch detector 120 of FIG. 1 and/ortouch detector 202 of FIG. 2. At 402, a signal that can be used topropagate an active signal through a surface region is sent. In someembodiments, sending the signal includes driving (e.g., using driver 214of FIG. 2) a transmitter such as a transducer (e.g., transmitter 104 ofFIG. 1) to propagate an active signal (e.g., acoustic or ultrasonic)through a propagating medium with the surface region. In someembodiments, the signal includes a sequence selected to optimizeautocorrelation (e.g., resulting in narrow/short peaks) of the signal.For example, the signal includes a Zadoff-Chu sequence. In someembodiments, the signal includes a pseudorandom binary sequence with orwithout modulation. In some embodiments, the propagated signal is anacoustic signal. In some embodiments, the propagated signal is anultrasonic signal (e.g., outside the range of human hearing). Forexample, the propagated signal is a signal above 20 kHz (e.g., withinthe range between 80 kHz to 100 kHz). In other embodiments, thepropagated signal may be within the range of human hearing. In someembodiments, by using the active signal, a user input on or near thesurface region can be detected by detecting disturbances in the activesignal when it is received by a sensor on the propagating medium. Byusing an active signal rather than merely listening passively for a usertouch indication on the surface, other vibrations and disturbances thatare not likely associated with a user touch indication can be moreeasily discerned/filtered out. In some embodiments, the active signal isused in addition to receiving a passive signal from a user input todetermine the user input.

In some embodiments, sending the signal includes determining the signalto be transmitted by a transmitter such that the signal isdistinguishable from other signal(s) transmitted by other transmitters.In some embodiments, sending the signal includes determining a phase ofthe signal to be transmitted (e.g., utilize code divisionmultiplexing/CDMA). For example, an offset within a pseudorandom binarysequence to be transmitted is determined. In this example, eachtransmitter (e.g., transmitters 104, 106, 108, and 110 of FIG. 1)transmits a signal with the same pseudorandom binary sequence but with adifferent phase/offset. The signal offset/phase difference between thesignals transmitted by the transmitters may be equally spaced (e.g.,64-bit offset for each successive signal) or not equally spaced (e.g.,different offset signals). The phase/offset between the signals may beselected such that it is long enough to reliably distinguish betweendifferent signals transmitted by different transmitters. In someembodiments, the signal is selected such that the signal isdistinguishable from other signals transmitted and propagated throughthe medium. In some embodiments, the signal is selected such that thesignal is orthogonal to other signals (e.g., each signal orthogonal toeach other) transmitted and propagated through the medium.

In some embodiments, sending the signal includes determining a frequencyof the signal to be transmitted (e.g., utilize frequency divisionmultiplexing/FDMA). For example, a frequency range to be utilized forthe signal is determined. In this example, each transmitter (e.g.,transmitters 104, 106, 108, and 110 of FIG. 1) transmits a signal in adifferent frequency range as compared to signals transmitted by othertransmitters. The range of frequencies that can be utilized by thesignals transmitted by the transmitters is divided among thetransmitters. In some cases if the range of frequencies that can beutilized by the signals is small, it may be difficult to transmit all ofthe desired different signals of all the transmitters. Thus the numberof transmitters that can be utilized with frequency divisionmultiplexing/FDMA may be smaller than can be utilized with code divisionmultiplexing/CDMA.

In some embodiments, sending the signal includes determining a timing ofthe signal to be transmitted (e.g., utilize time divisionmultiplexing/TDMA). For example, a time when the signal should betransmitted is determined. In this example, each transmitter (e.g.,transmitters 104, 106, 108, and 110 of FIG. 1) transmits a signal indifferent time slots as compared to signals transmitted by othertransmitters. This may allow the transmitters to transmit signals in around-robin fashion such that only one transmitter isemitting/transmitting at one time. A delay period may be insertedbetween periods of transmission of different transmitters to allow thesignal of the previous transmitter to sufficiently dissipate beforetransmitting a new signal of the next transmitter. In some cases, timedivision multiplexing/TDMA may be difficult to utilize in cases wherefast detection of touch input is desired because time divisionmultiplexing/TDMA slows down the speed of transmission/detection ascompared to code division multiplexing/CDMA.

At 404, the active signal that has been disturbed by a disturbance ofthe surface region is received. The disturbance may be associated with auser touch indication. In some embodiments, the disturbance causes theactive signal that is propagating through a medium to be attenuatedand/or delayed. In some embodiments, the disturbance in a selectedportion of the active signal corresponds to a location on the surfacethat has been indicated (e.g., touched) by a user.

At 406, the received signal is processed to at least in part determine alocation associated with the disturbance. In some embodiments,determining the location includes extracting a desired signal from thereceived signal at least in part by removing or reducing undesiredcomponents of the received signal such as disturbances caused byextraneous noise and vibrations not useful in detecting a touch input.In some embodiments, components of the received signal associated withdifferent signals of different transmitters are separated. For example,different signals originating from different transmitters are isolatedfrom other signals of other transmitters for individual processing. Insome embodiments, determining the location includes comparing at least aportion of the received signal (e.g., signal component from a singletransmitter) to a reference signal (e.g., reference signal correspondingto the transmitter signal) that has not been affected by thedisturbance. The result of the comparison may be used with a result ofother comparisons performed using the reference signal and othersignal(s) received at a plurality of sensors. The location, in someembodiments, is a location (e.g., a location coordinate) on the surfaceregion where a user has provided a touch input. In addition todetermining the location, one or more of the following informationassociated with the disturbance may be determined at 406: a gesture,simultaneous user indications (e.g., multi-touch input), a time, astatus, a direction, a velocity, a force magnitude, a proximitymagnitude, a pressure, a size, and other measurable or derivedinformation. In some embodiments, the location is not determined at 406if a location cannot be determined using the received signal and/or thedisturbance is determined to be not associated with a user input.Information determined at 406 may be provided and/or outputted.

Although FIG. 4 shows receiving and processing an active signal that hasbeen disturbed, in some embodiments, a received signal has not beendisturbed by a touch input and the received signal is processed todetermine that a touch input has not been detected. An indication that atouch input has not been detected may be provided/outputted.

FIG. 5 is a flow chart illustrating an embodiment of a process fordetermining a location associated with a disturbance on a surface. Insome embodiments, the process of FIG. 5 is included in 406 of FIG. 4.The process of FIG. 5 may be implemented in touch detector 120 of FIG. 1and/or touch detector 202 of FIG. 2.

At 502, a received signal is conditioned. In some embodiments, thereceived signal is a signal including a pseudorandom binary sequencethat has been freely propagated through a medium with a surface that canbe used to receive a user input. For example, the received signal is thesignal that has been received at 404 of FIG. 4. In some embodiments,conditioning the signal includes filtering or otherwise modifying thereceived signal to improve signal quality (e.g., signal-to-noise ratio)for detection of a pseudorandom binary sequence included in the receivedsignal and/or user touch input. In some embodiments, conditioning thereceived signal includes filtering out from the signal extraneous noiseand/or vibrations not likely associated with a user touch indication. Insome embodiments, the received signal is a signal of a signaltransmitter that has been selectively isolated from signals emitted byother transmitters.

At 504, an analog to digital signal conversion is performed on thesignal that has been conditioned at 502. In various embodiments, anynumber of standard analog to digital signal converters may be used. Theresulting digital signal is used to perform a first correlation at 506.In some embodiments, components of the received signal associated withdifferent signals/transmitters are separated. For example, differentsignals originating from different transmitters are isolated from othersignals of other transmitters. In some embodiments, performing the firstcorrelation includes correlating at least a portion of the convertedsignal (e.g., signal component from a single transmitter) with areference signal (e.g., corresponding reference signal of the signaltransmitter signal). Performing the correlation includescross-correlating or determining a convolution (e.g., interferometry) ofthe converted signal with a reference signal to measure the similarityof the two signals, as a time-lag is applied to one of the signals. Byperforming the correlation, the location of a portion of the convertedsignal that most corresponds to the reference signal can be located. Forexample, a result of the correlation can be plotted as a graph of timewithin the received and converted signal (e.g., time-lag between thesignals) vs. a measure of similarity. The associated time value of thelargest value of the measure of similarity corresponds to the locationwhere the two signals most correspond. By comparing this measured timevalue against a reference time value (e.g., at 306 of FIG. 3) notassociated with a touch indication disturbance, a time delay/offset orphase difference caused on the received signal due to a disturbancecaused by a touch input can be determined. In some embodiments, bymeasuring the amplitude/intensity difference of the received signal atthe determined time vs. a reference signal, a force associated with atouch indication may be determined. In some embodiments, the referencesignal is determined based at least in part on the signal that waspropagated through a medium (e.g., based on a source pseudorandom binarysequence signal that was propagated). In some embodiments, the referencesignal is at least in part determined using information determinedduring calibration at 306 of FIG. 3. The reference signal may be chosenso that calculations required to be performed during the correlation maybe simplified. For example, the reference signal used in 506 is asimplified reference signal that can be used to efficiently correlatethe reference signal over a relatively large time difference (e.g.,lag-time) between the received and converted signal and the referencesignal.

At 508, a second correlation is performed based on a result of the firstcorrelation. Performing the second correlation includes correlating(e.g., cross-correlation or convolution similar to step 506) at least aportion of the converted signal in 504 with a second reference signal.The second reference signal is a more complex/detailed (e.g., morecomputationally intensive) reference signal as compared to the firstreference signal used in 506. In some embodiments, the secondcorrelation is performed in 508 because using the second referencesignal in 506 may be too computationally intensive for the time intervalrequired to be correlated in 506. Performing the second correlationbased on the result of the first correlation includes using one or moretime values determined as a result of the first correlation. Forexample, using a result of the first correlation, a range of likely timevalues (e.g., time-lag) that most correlate between the received signaland the first reference signal is determined and the second correlationis performed using the second reference signal only across thedetermined range of time values to fine tune and determine the timevalue that most corresponds to where the second reference signal (and,by association, also the first reference signal) matched the receivedsignal. In various embodiments, the first and second correlations havebeen used to determine a portion within the received signal thatcorresponds to a disturbance caused by a touch input at a location on asurface of a propagating medium. In other embodiments, the secondcorrelation is optional. For example, only a single correlation step isperformed.

At 510, a result of the second correlation is used to at least in partdetermine a location associated with a disturbance. In some embodiments,determining the location includes comparing a determined time valuewhere the signals of the second correlation are most correlated andcomparing the determined time value with a reference time value (e.g.,determined at 306 of FIG. 3) not associated with a touch inputdisturbance, to determine a time delay/offset or phase difference causedon at least a portion of the received signal due to the disturbance(e.g., caused by a touch input). In some embodiments, this time delayassociated with a first signal transmitted by a first transmitter andreceived at a first receiver/sensor is compared with other determinedtime delays of different signals transmitted by other transmitters andreceived at the first receiver/sensor and other determined time delaysof the first signal transmitted by the first transmitter and received atother receivers/sensors to calculate a location of the disturbancerelative to the locations of the transmitters and/or sensors. By usingthe location of the transmitters/sensors relative to a surface of amedium that has propagated the received signal, a location on thesurface where the disturbance originated may be determined.

FIG. 6 is a flowchart illustrating an embodiment of a process fordetermining a location associated with a disturbance. In someembodiments, the process of FIG. 6 is included in 510 of FIG. 5. At 602,a plurality of results of correlations performed on a plurality ofsignals disturbed by a disturbance of a surface is received. Forexample, a result of the correlation performed at 508 of FIG. 5 isreceived. In some embodiments, a signal is propagated using transmitter104 and sensors 114, 116, and 118 each receives the propagated signalthat has been disturbed by a touch input on or near a surface of medium102 of FIG. 1. In some embodiments, each transmitter (e.g., transmitters104, 106, 108, and 110 of FIG. 1) of a touch input medium transmits adistinguishable signal that has been disturbed by a touch input and thedistinguishable signals are each received at sensors (e.g., sensors 112,114, 116, and 118 of FIG. 1) of the touch input medium for analysis.

The propagated signal may contain a predetermined signal and thepredetermined signal is received at the various sensors. Each of thereceived signals is correlated with a reference signal to determine theresults received at 602. In some embodiments, the received results areassociated with a same signal content (e.g., same binary sequence) thathas been freely propagated on a medium at the same time. In someembodiments, the received results are associated with different signalcontents that have been disturbed by the same disturbance. In someembodiments, the received signal at a receiver/sensor includescomponents of a plurality of distinguishable signals transmitted bydifferent transmitters and the received signal is separated intodifferent received signals each corresponding to a transmitted signal ofa signal transmitter for individual analysis to at least in partdetermine the results received at 602.

At 604, time differences associated with the plurality of results areused to determine a location associated with the disturbance. In someembodiments, each of the time differences is associated with a time whensignals used in the correlation are most correlated. In someembodiments, the time differences are associated with a determined timedelay/offset or phase difference caused on the received signal due tothe disturbance. This time delay may be calculated by comparing a timevalue determined using a correlation with a reference time value that isassociated with a scenario where a touch input has not been specified.The result of the comparison may be used to calculate a location of thedisturbance relative to the locations of transmitters and/or sensorsthat received the plurality of signals. By using the location of thetransmitters and/or sensors relative to a surface of a medium that haspropagated the received signal, a location on the surface where thedisturbance originated may be determined.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A system for detecting a location of a touchinput, comprising: a plurality of transmitters coupled to a propagatingmedium and each configured to emit a signal that is distinguishable fromother signals emitted from other transmitters, wherein the plurality oftransmitters are configured to emit the distinguishable signals throughthe propagating medium such that at least a portion of each of thedistinguishable signals emitted from the plurality of transmitterspropagate through the propagating medium without being directly guidedby reflectors in only parallel directions on a touch input area of thepropagating medium and a signal timing associated with each of thedistinguishable signals is different from other of the distinguishablesignals to distinguish each of the distinguishable signals from eachother; and a receiver coupled to the propagating medium and configuredto receive the signals from the transmitters to detect the location ofthe touch input on a surface of the propagating medium as indicated byan effect of the touch input on each of the distinguishable signals,wherein the receiver is configured to receive the signals from thetransmitters at least in part by being configured to receive a combinedsignal that includes at least a portion of each of the distinguishablesignals disturbed by at least the same touch input at the location, eachof the distinguishable signals associated with the different signaltiming from other of the distinguishable signals have been separatelytransmitted by a different transmitter of the plurality of transmitters,and the received combined signal is processed to separately identifyeach of the included portions of the distinguishable signals from thereceived combined signal, and the each of the included portions of thedistinguishable signals that has been separately identified correspondsto at least a same single contact of the touch input provided at thesame location, and for each of the separately identified includedportions of the distinguishable signals, which specific correspondingtransmitter of the plurality of transmitters transmitted thecorresponding distinguishable signal and a corresponding relativelocation of the specific corresponding transmitter are identified foruse in determining the location of the touch input.
 2. The system ofclaim 1, wherein at least one of the received signals is correlated witha corresponding expected signal without the touch input to determine theeffect of the touch input on the at least one received signal.
 3. Thesystem of claim 1, wherein the different signal timings associated withthe distinguishable signals emitted by the transmitters are associatedwith different signal phases.
 4. The system of claim 1, wherein emittingthe signals of the transmitters includes utilizing code divisionmultiplexing to distinguish the emitted signals.
 5. The system of claim1, wherein the signals emitted by the transmitters are distinguishablefrom each other including by varying a frequency range of the signalsemitted by the transmitters from each other emitted signal.
 6. Thesystem of claim 1, wherein emitting the signals of the transmittersincludes utilizing frequency division multiplexing to distinguish theemitted signals.
 7. The system of claim 1, wherein each of thedistinguishable signals ultrasonically encodes a different binary datafrom other of the distinguishable signals.
 8. The system of claim 1,wherein emitting the signals of the transmitters includes utilizing timedivision multiplexing to distinguish the emitted signals.
 9. The systemof claim 1, wherein emitting the signal that is distinguishable fromother signals emitted from other transmitters includes offsetting thesignal from the other signals emitted from other transmitters.
 10. Thesystem of claim 1, wherein emitting the signal that is distinguishablefrom other signals emitted from other transmitters includes offsetting apseudorandom binary sequence included in the signal by a predeterminednumber of bits from a pseudorandom binary sequence included in the othersignals emitted by other transmitters.
 11. The system of claim 10,wherein a relative offset amount between a first signal and a secondsignal emitted by one or more of the transmitters is equal to a relativeoffset amount between the second signal and a third signal emitted byone or more of the transmitters.
 12. The system of claim 1, wherein thesignals emitted by the transmitters are orthogonal to each other signal.13. The system of claim 1, wherein the effect of the touch input on eachof the distinguishable signals includes a delay caused on each of thedistinguishable signals by the touch input.
 14. The system of claim 13,wherein detecting the location includes comparing the delay of each ofthe distinguishable signals.
 15. The system of claim 1, wherein thetouch input is associated with one or more of the following: a locationcoordinate, a gesture, a time, a status, a direction, a velocity, aforce magnitude, a proximity magnitude, a pressure, and a size.
 16. Thesystem of claim 1, wherein at least one of the distinguishable signalsincludes a Zadoff-Chu sequence.
 17. The system of claim 1, whereindetecting the location of the touch input includes comparing each of theseparated distinguishable signals with a corresponding reference signalto determine comparison results and comparing one of the comparisonresults of one of the received distinguishable signals with another oneof the comparison results of another one of the received distinguishablesignals.
 18. A method for detecting a location of a touch input,comprising: emitting from each of a plurality of transmitters coupled toa propagating medium a signal that is distinguishable from other signalsemitted from other transmitters, wherein the distinguishable signals areemitted through the propagating medium such that at least a portion ofeach of the distinguishable signals emitted from the plurality oftransmitters propagate through the propagating medium without beingdirectly guided in only parallel directions by reflectors and a signaltiming associated with each of the distinguishable signals is differentfrom other of the distinguishable signals to distinguish each of thedistinguishable signals from each other; receiving from at least onereceiver coupled to the propagating medium the signals from thetransmitters to detect the location of the touch input on a surface ofthe propagating medium as indicated by an effect of the touch input oneach of the distinguishable signals, wherein receiving the signals fromthe transmitters includes receiving a combined signal that includes atleast a portion of each of the distinguishable signals disturbed by atleast the same touch input at the location, and each of thedistinguishable signals associated with the different signal timing fromother of the distinguishable signals have been separately transmitted bya different transmitter of the plurality of transmitters; and processingthe received combined signal to separately identify each of the includedportions of the distinguishable signals from the received combinedsignal, wherein the each of the included portions of the distinguishablesignals that has been separately identified corresponds to at least asame single contact of the touch input provided at the same location,and for each of the separately identified included portions of thedistinguishable signals, which specific corresponding transmitter of theplurality of transmitters transmitted the corresponding distinguishablesignal and a corresponding relative location of the specificcorresponding transmitter are identified for use in determining thelocation of the touch input.
 19. The method of claim 18, furthercomprising comparing each of the separated distinguishable signals witha corresponding reference signal to determine comparison results andcomparing one of the comparison results of one of the receiveddistinguishable signals with another one of the comparison results ofanother one of the received distinguishable signals.
 20. A computerprogram product for detecting a location of a touch input, the computerprogram product being embodied in a non-transitory computer readablestorage medium and comprising computer instructions for: emitting fromeach of a plurality of transmitters coupled to a propagating medium asignal that is distinguishable from other signals emitted from othertransmitters, wherein the distinguishable signals are emitted throughthe propagating medium such that at least a portion of each of thedistinguishable signals emitted from the plurality of transmitterspropagate through the propagating medium without being directly guidedin only parallel directions by reflectors and a signal timing associatedwith each of the distinguishable signals is different from other of thedistinguishable signals to distinguish each of the distinguishablesignals from each other; receiving from at least one receiver coupled tothe propagating medium the signals from the transmitters to detect thelocation of the touch input on a surface of the propagating medium asindicated by an effect of the touch input on each of the distinguishablesignals, wherein receiving the signals from the transmitters includesreceiving a combined signal that includes at least a portion of each ofthe distinguishable signals disturbed by at least the same touch inputat the location, and each of the distinguishable signals associated withthe different signal timing from other of the distinguishable signalshave been separately transmitted by a different transmitter of theplurality of transmitters; and processing the received combined signalto separately identify each of the included portions of thedistinguishable signals from the received combined signal, wherein theeach of the included portions of the distinguishable signals that hasbeen separately identified corresponds to at least a same single contactof the touch input provided at the same location, and for each of theseparately identified included portions of the distinguishable signals,which specific corresponding transmitter of the plurality oftransmitters transmitted the corresponding distinguishable signal and acorresponding relative location of the specific correspondingtransmitter are identified for use in determining the location of thetouch input.